Semiconductor substrates such as wafers are often processed in processing lines, which generally comprise a number of stations. One such station is depicted in FIG. 1 and generally indicated at 10. The station 10 comprises a transfer chamber 11 with a suitable platform (not shown). Several process chambers (four in this example) 12 are mounted at four facets of the transfer chamber 11, which, in this example, has six facets. Two load lock chambers 13 are mounted on two other facets of the transfer chamber and connected to the mini-environment (also called Factory Interface, FI) 15, which is also shown in FIG. 2. A robot schematically indicated at 14 operates to transfer the wafers from the load lock chambers 13 to and between the process chambers 12. Examples of such a station are the Centura or Endura, available from Applied Materials, Inc of Santa Clara, Calif.
The mini-environment, generally indicated at 15, serves as a clean environment for wafer scheduling and handling. Such a mini-environment may be a SMIF-300 Wafer Management System available from Asyst Technologies, Inc. of Fremont, Calif. It includes an enclosure 16 and several (two in this example) wafer pod loaders 21 and 22 for wafer pods 23 and 24 (FIG. 2), respectively. Each wafer pod 23, 24 contains a stack of wafers to be processed by the station 10. The enclosure 16 houses one or more robots (two in this example) 25 and 27 for transferring the wafers 28 from the pods to the load lock chamber 13. A suitable track robot is available from Equipe Technologies of Sunnyvale, Calif. The robot 27,29 is also used to transfer wafers to and from the wafer aligner 18.
The workstations could be differently structured and, for instance, comprise other elements, such as a buffer chamber, pre-clean and cool-down chambers, pre-processing and post-processing chambers, and so on.
The transformation of wafer disks into integrated circuit chips often involves several steps where the disks are repeatedly processed, stored and transported. Due to the delicate nature of the disks and their extreme value, it is preferred that they are properly protected throughout this procedure from contaminants. One purpose of a wafer carrier is to provide protection from these contaminants. One type of wafer carrier referred to as a pod or box can completely enclose the wafers to facilitate such protection. The wafer pods 23, 24 depicted in FIG. 2 illustrate one example of such a wafer pod which is often formed primarily of plastic.
Since the processing of wafer disks is generally automated, it is preferred for the pod or carrier to precisely align the wafer disks according to the specifications of the processing equipment being used. To seat and align the pods 23, 24, each wafer pod loader 21, 22 has a load-port 30, 31 through which the robots 25,27 transfer the wafers from the pods to the load lock chambers. The tolerances available for aligning the pods or other carriers are generally very tight, such as around 0.20 mm, for example, for proper interaction between the processing equipment and the wafer disks. Internationally recognized standards have been published which specify many of these tolerances. For example, the SEMI (Semiconductor Equipment and Materials International, formerly known as Semiconductor Equipment and Materials Institute) E47.1-0699 standard partially specifies the boxes and pods used to transport and store 300 mm wafers in an IC manufacturing facility.
One pod or box which complies with E47.1 is known as the Front-Opening Univerisal Pod (FOUP) and has a non-removable cassette and a front-opening interface that mates with a load-port that complies with SEMI E62, entitled “Provisional Specification for 300 mm Front-Opening Interface Mechanical Standard (FIMS).” More specifically, the pod has a door positioned on the front side of the pod, which corresponds to the front side of the cassette where wafers are accessed. In this standard, the pod door is perpendicular to the wafers and parallel to a specified facial datum plane so that the door and its frame can mate with an FIMS port that conforms to SEMI E62. For proper mating, the door and its frame should have surfaces that mate with the seal zones and the reserved spaces for vacuum application defined in SEMI E62 as well as properly latch to the port. The doors and walls of the pod are typically fabricated from plastic.
The physical alignment mechanism from the pod to the tool load-port (or a nest on a handler) includes receptacles such as those indicated at 100a-100c (in phantom) in FIGS. 10 and in FIGS. 11a-11b, which are located on the bottom wall 102 of each pod such as a pod 103. Typically, the receptacles are molded or cast or cast from plastic integrally with the bottom wall of the pod. Alternatively, each receptacle may be formed separately and attached to the under side of the pod wall 102. Suitable fasteners such as rivets, bolts or screws may be passed through a flange on each side of the receptacle to secure the receptacle to the underside of the pod. The receptacles may also be glued or welded to the pod underside.
As best seen in FIGS. 11a-11b, each of the pod receptacles as represented by receptacle 100a, has a generally inverted V-shaped groove 108 formed in the underside of the receptacle and positioned to mate with a kinematic coupling pin such as pin 110a disposed on a support plate 111 of a tool load-port. The receptacles 100a-100c are intended to mate with three or six such coupling pins as specified in SEMI E57 entitled “Provisional Mechanical Specification for Kinematic Couplings Used to Align and Support 300 mm Wafer Carriers,” 1997; 1990, which is incorporated by reference in its entirety. In SEMI E57, it is recommended that each of the V-shaped grooves extend along a line that is perpendicular to and co-planar with the nominal wafer centerline as shown in FIG. 10. The grooves are intended to provide adequate alignment even when the grooves are shrunken or slightly misaligned (such as when they do not all line up with the nominal wafer center line).
As best seen in FIG. 10, the SEMI E57 standard has defined three sets of kinematic coupling pin locations with two possible pin locations in each set. A pin located in the outer position is designated a primary pin and is indicated at 110a. In a conventional load-port, each load-port would have three such primary pins 110a-110c arranged in a triangle pattern as shown in FIG. 10. The three primary kinematic coupling pins form a nest 112 on which the receptacles 100a-100c of a pod may be placed as shown in phantom in FIG. 10.
Each set of possible pin locations also includes an inner location. A pin located in the inner position is designated a secondary pin and is indicated in phantom at 110d-110f. In a conventional pod handler or other transport robot or load-port, the handler could have three such secondary pins 110d-110f arranged in a triangle pattern to form a nest on which the receptacles 100a-100c of a pod may be placed as shown in phantom in FIG. 10. The location of each primary and secondary pin is specified with respect to three orthogonal datum planes defined in SEMI E57: the horizontal datum plane, the facial datum plane, and the bilateral datum plane.
The shape of these prior kinematic coupling pins is also specified in SEMI E57. As set forth therein and best seen in FIGS. 11a and 11b, each pin 110a-110c (or 110d-110f) is radially symmetric about its vertical center axis line 120. Each pin includes a generally cylindrical base portion 122 and a generally spherical top portion 124 disposed at the top of the pin. The spherical top portion 124 is shaped to facilitate contact with a flat plate. Disposed between the spherical portion 124 and the cylindrical portion 122 is an intermediate rounded frusto-conical surface 126 which is shaped to facilitate contact with angled mating surfaces. The rounded surface 126 has radii of curvature as indicated by radii 130a and 130b. 
Other mating schemes are also contemplated within SEMI E57, such as a pyramid-shaped opening in a wafer carrier receptacle. It is also contemplated that front-opening boxes and pods may need to contact the pins on the side to provide pressure against a front mechanical interface. When designing the mating features of the receptacles on the bottom of the wafer carriers, SEMI E57 recommends that designers follow the recommendations given in the book entitled “Precision Machine Design” by Dr. Alexander H. Slocum, Society of Manufacturing Engineers, Item Code 2597, 1992 (originally published by Prentice-Hall, 1992).